TWI568701B - Selective bacteriostatic method of sulfate-reducing bacteria - Google Patents

Description

Selective bacteriostatic method for sulfate reducing bacteria

The present invention relates to a selective bacteriostatic method for a sulphate-reducing bacterium which inhibits the proliferation of a sulfate-reducing bacterium without inhibiting the proliferation of other bacteria. Further, the present invention relates to a gypsum composition, a gypsum-based solidified material, and a gypsum-based building material which can suppress the generation of hydrogen sulfide using gypsum as a sulfur source.

A sulfate-reducing strain is a bacterium which oxidizes an organic substance with a sulfate ion as an electron acceptor to obtain energy. The above-mentioned sulfuric acid reducing bacteria have different growth temperature regions depending on the type, and there are high temperature bacteria, medium temperature bacteria, low temperature bacteria and good cold bacteria. Further, depending on the pH of the growth, there are bacteria which grow well in the vicinity of neutrality and bacteria which grow well under acidic or alkaline conditions. In addition, the living area is also spread over a wide area such as marine mud, general soil, hot spring spouts, and pipelines.

In the process of obtaining energy of the sulfate reducing bacteria, hydrogen sulfide is produced as a reducing body of sulfate ions. Since this hydrogen sulfide is a substance which is toxic or corrosive and emits malodor, it is a problem if it is produced in a large amount. For example, when sulfuric acid reducing bacteria obtain energy by using sulfate ions contained in natural water, fertilizer (ammonium sulfate, etc.) as an electron acceptor, hydrogen sulfide is generated, which hinders the growth of crops in farmland. Or iron (buried) Tube, etc.) corrosion.

Moreover, in recent years, the case where hydrogen sulfide is generated by using the illegally discarded gypsum as a sulfur source has become a problem. It is known that the production of hydrogen sulfide is related to sulfuric acid reducing bacteria.

As an example of the generation of hydrogen sulfide caused by the above-mentioned sulfuric acid reducing bacteria, it is reported that hydrogen sulfide is generated from waste gypsum board. The waste gypsum board contains a paste or paper (nutrient) in addition to calcium sulfate (sulfate ion) as a main component. Therefore, there is a case where the sulfuric acid reducing bacteria in the soil anabolize the waste gypsum board to generate hydrogen sulfide.

Therefore, attempts have been made to inhibit the growth of sulfuric acid reducing bacteria and to suppress the formation of hydrogen sulfide. For example, the applicant of the present invention has disclosed a method of suppressing the growth of sulfuric acid-reducing bacteria and suppressing the formation of hydrogen sulfide by adding a cerium compound to a soil-treating material mainly composed of gypsum (see Patent Document 1).

However, the technique described in Patent Document 1 uses a very expensive ruthenium compound, and thus has a problem in terms of manufacturing cost. Especially in the use of a large amount of materials such as soil treatment materials, there is a fact that cost becomes an obstacle and cannot be expanded.

Therefore, the applicant of the present application also discloses the method of adding aluminum sulfate hydrate [Al ₂ (SO ₄ ) ₃ ‧nH ₂ O (n=6, 10, 16, 18, 27)] to the gypsum composition] When a specific aluminum compound is used, the proliferation of the sulfate-reducing bacteria is inhibited, and the formation of hydrogen sulfide is suppressed (see Patent Document 2).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2002-177992

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2010-208870

The method described in Patent Document 2 uses an aluminum compound which is inexpensive and easily available as a bismuth compound, and therefore solves the problem of the manufacturing cost of the technique described in Patent Document 1. However, there is still room for improvement in the following areas.

In other words, according to the method described in Patent Document 2, the growth of the sulfate-reducing bacteria can be suppressed, and the formation of hydrogen sulfide can be suppressed. However, the growth of bacteria other than the sulfate-reducing bacteria (hereinafter referred to as "other bacteria") can be inhibited. situation. When the proliferation of other bacteria is suppressed, there is a case where the microorganisms such as soil are destroyed and problems such as malodor and plant growth are hindered. Therefore, it is desired to establish a method for selectively inhibiting the proliferation of sulfate-reducing bacteria without inhibiting the proliferation of other bacteria.

The present invention has been made to solve the problems of the above-described prior art. That is, the present invention provides a selective bacteriostatic method, gypsum composition, gypsum-based solidified material, and gypsum-based building material, which can selectively inhibit the proliferation of sulfate-reducing bacteria without inhibiting the proliferation of other bacteria.

As a result of intensive studies on the above-mentioned problems, the inventors of the present invention have found that chelated Al has an effect of selectively inhibiting the proliferation of sulfate-reducing bacteria, and has completed the present invention.

[1] Selective bacteriostatic method for sulfate reducing bacteria:

That is, according to the present invention, there is provided a selective bacteriostatic method for sulphate-reducing bacteria, which comprises selectively inhibiting the proliferation of the sulphate-reducing bacteria by allowing chelating Al to coexist in an environment in which sulfuric acid-reducing bacteria are present .

In the method of the present invention, it is preferred to add an Al ³⁺ source and a chelating agent to the environment in which the sulfuric acid reducing bacteria are present, thereby producing the chelated Al in the above environment. Further, in the method of the present invention, the Al ³⁺ source is preferably at least one selected from the group consisting of Al ₂ O ₃ , AlCl ₃ , Al(OH) ₃ and Al ₂ (SO ₄ ) ₃ . . Further, in the method of the present invention, the sulfuric acid reducing bacteria are preferably bacteria which survive in the middle temperature range (20 to 45 ° C) and in the neutral range (pH 5 to 9).

[2] Gypsum composition:

Moreover, according to the present invention, there is provided a gypsum composition comprising gypsum (A) and chelated Al (B) in an amount of 0.01 to 20 parts by mass based on 100 parts by mass of the gypsum (A). The range contains the above chelated Al(B).

In the composition of the present invention, it is preferred to contain an Al ³⁺ source (b-1) and a chelating agent (b-2) instead of the above chelated Al(B). Further, in the composition of the present invention, the Al ³⁺ source (b-1) is preferably selected from the group consisting of Al ₂ O ₃ , AlCl ₃ , Al(OH) ₃ and Al ₂ (SO ₄ ) ₃ . At least one of the Al compounds.

In the composition of the present invention, it is preferred that part or all of the gypsum is waste gypsum, and it is preferred that part or all of the gypsum is calcined gypsum.

[3] Gypsum-based solidified materials, gypsum-based building materials:

Further, according to the present invention, there is provided a gypsum-based solidified material comprising a part or all of the gypsum of the gypsum composition as a calcined gypsum. Moreover, according to the present invention, there is provided a gypsum-based building material which is obtained by adding water, molding, and curing a part or all of the gypsum in the gypsum composition.

The selective bacteriostatic method and gypsum composition of the present invention may optionally be Inhibition of the proliferation of sulfate-reducing bacteria. Therefore, the proliferation of the sulfate-reducing bacteria can be suppressed, and the formation of hydrogen sulfide can be suppressed. On the other hand, the selective bacteriostatic method and the gypsum composition of the present invention do not inhibit the proliferation of other bacteria, and therefore do not destroy the microbial phase such as soil, and there is no problem such as occurrence of malodor and hindering plant growth.

Fig. 1 is a graph showing the results of evaluating the effect of inhibiting the growth of sulfate-reducing bacteria of chelating Al.

Fig. 2 is a graph showing the results of evaluating the effect of inhibiting the growth of Escherichia coli chelating Al.

Fig. 3 is a graph showing the results of evaluating the growth inhibitory effect of the chelating Al butyric acid bacteria.

Fig. 4 is a graph showing the results of evaluating the growth inhibitory effect of the sulfate-reducing bacteria of AlCl ₃ .

Fig. 5 is a graph showing the results of evaluation of the growth inhibitory effect of Escherichia coli on AlCl ₃ .

Fig. 6 is a graph showing the results of evaluating the growth inhibitory effect of butyric acid bacteria of AlCl ₃ .

Hereinafter, the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and includes all objects having the limitations of the invention.

[1] Selective bacteriostatic method for sulfate reducing bacteria:

The present invention relates to a selective bacterium for selectively inhibiting the proliferation of a sulfate reducing bacteria method.

As described above, the "sulfuric acid-reducing bacteria" are bacteria which oxidize organic substances with sulfate ions as electron acceptors to obtain energy. The bacteria are widely distributed in anaerobic environments such as general soil or sewage sludge. The type of the sulfate reducing bacteria to be applied to the present invention is not particularly limited. For example, it may be a Gram-negative bacteria, a Gram-positive bacteria, or an archaea.

Specific examples include: Desulfovibrio; Gram-negative anaerobic bacterium, Gram-negative anaerobic Helicobacter, Desulfuromonas; Gram-negative anaerobic Actinomycetes, Gram-negative anaerobic spirochetes, Desulfitobacterium; Gram-negative anaerobic bacteria, Desulfotomaculum; Gram-positive endogenous neutrophils ) and other sulfate reducing bacteria.

Specific examples of the bacteria belonging to the genus Desulfovibrio include: Desulfovibrio vulgaris, Desulfovibrio africanus, Desulfovibrio desulfuricans, and Vibrio cholerae (Desulfovibrio gigas) and so on. Specific examples of the bacteria belonging to the genus Defibrotolytic bacteria include Desulfotomaculum ruminis and the like.

The method of the present invention has an inhibitory effect on all of the above-mentioned sulfate-reducing bacteria, that is, against Gram-negative bacteria, Gram-positive bacteria, and archaea. Among them, sulfate reducing bacteria which survive in the medium temperature range (20 to 45 ° C) and the neutral range (pH 5 to 9) can be preferably used. It has been described that common desulfovation bacteria, African desulfovation bacteria, desulfurization and desulfurization bacteria, giant desulfovation bacteria, rumen desulfurization intestinal bacteria are "in the middle temperature range (20 ~ 45 ° C) and neutral domain Sulfate-reducing bacteria that survive in (pH 5~9).

The method of the present invention is understood to be that chelated Al acts on sulfate reducing bacteria The sulfuric acid reduction mechanism stops the sulfuric acid reduction mechanism of the sulfate reducing bacteria, and as a result, selectively inhibits the proliferation of the sulfuric acid reducing bacteria. The term "selective" means that the growth inhibitory effect is specific to the sulfate-reducing bacteria. In other words, it means that the growth inhibitory effect on the sulfate-reducing bacteria can be seen, but the growth inhibitory effect on the bacteria other than the sulfate-reducing bacteria (other bacteria) is hardly observed.

Representative examples of "other bacteria" include Escherichia coli (facultative anaerobic Gram-negative bacillus, Japanese name: coliform), and Clostridium butyricum (gram-positive endogenous cytoplasm). Forming bacilli, Japanese name: butyric acid bacteria, etc.

In the present invention, "bacterial" means inhibiting the proliferation of bacteria. That is, the degree of bacteria is directly reduced without sterilization or sterilization.

[1-1] Chelated Al:

The method of the present invention is characterized in that chelating Al is coexisted in an environment in which sulfuric acid reducing bacteria are present. The "environment in which the sulfate-reducing bacteria are present" is not particularly limited as long as the presence of the sulfate-reducing bacteria can be confirmed. For example, an anaerobic environment such as general soil or sewage sludge widely distributed by sulfuric acid reducing bacteria can be cited. The "chelated Al" is formed of Al ³⁺ and a chelating agent, and more specifically, is a complex of a chelating agent coordinated to Al ³⁺ which is a central ion. The chelated Al is rapidly formed by mixing an Al ³⁺ source described later with a chelating agent.

The "chelating agent" is a polydentate ligand which is bonded to Al ³⁺ to form a chelated Al. In the present invention, the type of the chelating agent is not particularly limited. For example, it may be a chain-like ligand or a cyclic ligand.

Examples of the chain-like ligand include polybasic carboxylic acids such as oxalic acid, malonic acid, tartaric acid, glutaric acid, malic acid, citric acid, and maleic acid (all of which are double-dentate ligands); Polyamines such as amines (EDA, double-dentate ligands); ethylenediaminetetraacetic acid (EDTA, A hexadentate ligand such as an aminopolycarboxylic acid; a bipyridine such as 2,2'-bipyridyl or 1,10-morpholine (both a double-dentate ligand).

Examples of the cyclic ligand include porphyrins (tetradentate ligands) and crown ethers (the coordination number varies depending on the compound. For example, 18-crown-6 is a hexadentate ligand).

Among the above chelating agents, a chelating agent in which Al ³⁺ is added to easily form a chelated Al is preferable. Further, the present invention is often practiced in a natural environment, and therefore, it is more preferably a chelating agent which does not adversely affect the environment. Specific examples thereof include citric acid, malonic acid, tartaric acid, glutaric acid, malic acid, and maleic acid.

The ratio of the amount of Al ³⁺ to the chelating agent is not particularly limited. Depending on the type of chelating agent, it differs from the molar ratio of Al ³⁺ forming a stable complex. However, it is preferred to adjust the amount of the chelating agent added (mol ratio) in such a manner that the total amount of the added Al ³⁺ source is chelated and Al ^{3+ is} dissolved. For example, the molar ratio of the Al ³⁺ source to the oxalic acid to form a stable complex is 1:3, and the molar ratio of the Al ³⁺ source to the citric acid to form a stable complex is 1:2, and the Al ³⁺ source and The molar ratio of EDTA to form a stable complex is 1:1.

Further, as will be described later, the chelated Al can be formed from an inexpensive and easily available aluminum compound, and the production cost can be made lower than in the case of using a ruthenium compound. In particular, when a 2 to 4 member organic acid which is inexpensive and easily available is used as a chelating agent, the effect of reducing the manufacturing cost is large.

[1-2] Al ³⁺ source:

Chelating Al can either add itself (ie, already chelating Al ³⁺ ) to the environment in which the sulfate-reducing bacteria are present, or add an Al ³⁺ source and a chelating agent to the above environment in the above environment. The above chelated Al is produced. That is, in the case where it is convenient to separately add the Al ³⁺ source and the chelating agent, the chelated Al is rapidly formed in the above environment.

The "Al ³⁺ source" is a substance which forms Al ^{3+ which is} a central ion of a chelate in the presence of water. The type of the specific substance is not particularly limited. Among them, at least one Al compound selected from the group consisting of Al ₂ O ₃ , AlCl ₃ , Al(OH) ₃ and Al ₂ (SO ₄ ) ₃ is preferable. Further, since it is "at least one kind", one type of the above compounds may be used alone, or two or more kinds of the above compounds may be used in combination.

Of the "Al ₂ O ₃ , AlCl ₃ , Al(OH) ₃ and Al ₂ (SO ₄ ) ₃ ", of course, these anhydrous substances are contained, and these hydrates are also contained. Further, the form of the compound may be crystalline or amorphous (for example, amorphous alumina or the like). Further, as such a compound, it is not necessary to use a pure substance, and a mixture can also be used. For example, minerals containing such compounds can also be used as the source of Al ³⁺ .

[2] Gypsum composition:

The gypsum composition of the present invention contains gypsum (A) as a main component, and is characterized in that it contains chelated Al(B) in addition to the gypsum (A), and is 100 parts by mass relative to gypsum (A). The chelated Al(B) is contained in a range of 0.01 to 20 parts by mass.

[2-1] Gypsum:

The "gypsum" in the present invention is a mineral containing calcium sulfate as a main component, and examples thereof include a 1/2 hydrate of calcium sulfate, a dihydrate, an anhydrate, and the like. Therefore, in the present invention, one type of the above-mentioned gypsum may be used alone or two or more types may be used in combination. The 1/2 hydrate of calcium sulfate (CaSO ₄ ‧1/2H ₂ O) is also referred to as hemihydrate gypsum or calcined gypsum. For example, β-type hemihydrate gypsum, α-type hemihydrate gypsum, etc. are mentioned.

Further, in the invention, it is preferred that part or all of the gypsum is calcined gypsum. In the "calcined gypsum" of the present invention, in addition to the above-mentioned hemihydrate gypsum, anhydrous calcium sulfate (CaSO ₄ , also known as soluble anhydrite or type III) which absorbs moisture in the air and is easily changed to hemihydrate gypsum is also included. Anhydrite gypsum).

Therefore, as the calcined gypsum in the present invention, one type of β-type hemihydrate gypsum, α-type hemihydrate gypsum, and type III anhydrite may be used alone, or two or more types may be used in combination.

Further, as the raw material gypsum of the calcined gypsum, any of natural products (hemihydrate gypsum <bassanite>, etc.), by-product gypsum, and waste gypsum can be used. Among them, in terms of production cost, promotion of recovery, environmental protection, and the like, it is preferred that part or all of the gypsum is waste gypsum.

[2-2] Chelated Al:

In the gypsum composition of the present invention, the chelated Al which is the same as the bacteriostatic method of the present invention described above can be used. The form of the chelating agent is not particularly limited. Among them, a powdery chelating agent is preferably used. Usually, as the main material of the gypsum composition of the present invention, gypsum, a powder is used. Therefore, it is easy to handle when a powdery chelating agent is used similarly to the said gypsum.

The gypsum composition of the present invention contains the above-mentioned chelated Al (B) in an amount of 0.01 to 20 parts by mass based on 100 parts by mass of the gypsum (A). When the content of the chelating Al is 0.01 parts by mass or more, the proliferation of the sulfate-reducing bacteria can be selectively inhibited without inhibiting the proliferation of other bacteria, and the generation of hydrogen sulfide can be suppressed. Further, the above effects can be obtained before the content of the chelated Al reaches 20 parts by mass.

However, it is preferable to contain chelated Al(B) in an amount of 0.1 to 10 parts by mass, and more preferably to contain chelated Al in a range of 0.2 to 2 parts by mass, based on 100 parts by mass of the gypsum (A). B). When the content of the chelating Al (B) is 0.1 part by mass or more, the generation of hydrogen sulfide can be more reliably suppressed. On the other hand, even if a large amount of chelated Al is added, the inhibitory effect is not increased in accordance with the amount. Therefore, by making the content of chelated Al(B) 10 parts by mass or less can prevent the manufacturing cost from rising beyond the demand.

[2-3] Al ³⁺ source:

The gypsum composition of the present invention also includes an Al ³⁺ source (b-1) and a chelating agent (b-2) in place of the chelated Al(B). Even if the Al ³⁺ source and the chelating agent are separately added, the chelating Al is rapidly formed in the gypsum composition by the added water during the production process or the use of the gypsum composition. As the Al ³⁺ source and the chelating agent, the same method as the bacteriostatic method of the present invention described above can be used.

[3] Gypsum-based solidified materials, gypsum-based building materials:

As described above, the gypsum composition of the present invention contains gypsum and chelated Al in a predetermined ratio. Therefore, the present invention includes all gypsum compositions satisfying the above composition. That is, its use is not limited. For example, a gypsum composition used in the use of a chemical reaction (hydration reaction) which does not utilize gypsum is also included in the scope of the present invention. Examples of the gypsum composition used in the use of the unfavorable hydration reaction include a wire for white wire used in a sports field, a fertilizer, a rubble treatment agent, and the like.

However, the gypsum composition of the present invention can be preferably used for the hydration reaction using gypsum, and specifically, it can be preferably used as a gypsum-based solidified material or a gypsum-based building material. The gypsum-based solidified material of the present invention is characterized in that it contains a part or all of the gypsum in the gypsum composition of the present invention as a calcined gypsum. Further, the gypsum-based building material according to the present invention is characterized in that it is obtained by adding water, forming and solidifying one or all of the gypsum in the gypsum composition of the present invention.

The calcined gypsum (hemihydrate gypsum. Also contains type III anhydrite) has a property of easily changing to dihydrate gypsum (CaSO ₄ ‧2H ₂ O) by a hydration reaction and forming a cured product having a high strength. Therefore, in the gypsum composition of the present invention, a part or all of the gypsum may be preferably used as a gypsum-based solidified material and a gypsum-based building material.

The gypsum-based solidified material and the gypsum-based building material of the present invention can selectively inhibit the growth of sulfuric acid reducing bacteria without inhibiting the proliferation of other bacteria, and can suppress the generation of hydrogen sulfide. Moreover, it has performance (strength, fire resistance, sound insulation, shock resistance, etc.) and construction workability comparable to those of the conventional gypsum-based solidified material or gypsum-based building material.

The gypsum-based solidified material may be formed by curing itself, or may be mixed with the other and solidified as a whole. For example, a wet material (gypsum-based wet coating material) such as a gypsum paste (coating material) or a gypsum board joint processing material (soot) may be used. For example, a solidified material for soil treatment (such as a gypsum-based soil improving material) for solidifying residual soil, sludge, soil, or the like can be used.

Examples of the gypsum-based building materials include gypsum boards, gypsum blocks, and the like used in ceiling materials, wall materials, flooring materials, and the like. The gypsum board includes, for example, a gypsum board coated with a base paper of a gypsum board through a base paper; a glass mat gypsum board covered with a glass fiber mat (sheet); the inside of the gypsum board (1 to 2 mm from the surface) The inside is a gypsum board in which a fiberglass mat (sheet) is embedded. Further, the use of the above gypsum board is not limited to the structure. For example, it can also be applied to a functional functional gypsum board for decoration, sound absorbing, and moisture absorption.

[4] Effects of the gypsum composition of the present invention, etc.:

The gypsum composition, the gypsum-based solidified material, and the gypsum-based building material of the present invention have an effect of selectively inhibiting the growth of other bacteria without inhibiting the proliferation of other bacteria in the presence of the sulfuric acid-reducing bacteria. The proliferation of the reducing bacteria inhibits the production of hydrogen sulfide.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples and comparative examples. However, the present invention is not limited to the configuration of the following embodiments. In addition, the "part" and "%" in the following description are the quality standards unless otherwise specified.

[1] Examples 1 to 3, Comparative Example 1 (selective bacteriostatic method): [pre-cultivation]

In the examples and comparative examples, the following strains which are representative standard strains were used. About Desulfovibrio vulgariss DSM 644 ^T was obtained from DSMZ (Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH), a standard strain storage facility in Germany. Other bacteria were obtained from the Biotechnology Center of the Product Evaluation Technology Foundation. For these strains, preculture was carried out using a medium designated by the distribution authority. The pre-culture period was set to about 1 week.

(1) Sulfate-reducing bacteria: Desulfovibrio vulgariss DSM 644 ^T

(2) Coliform: Escherichia coli NBRC 102203 ^T

(3) Butyric acid bacteria: Clostridium butyricum NBRC 13949 ^T

[subculture]

After the preculture, only the cells were recovered, and each of the bacteria was subcultured in the medium of the composition shown in Tables 1 to 3. The cells collected and washed after the above subculture were used in the examples and comparative examples. In addition, the "deionized water / Al aqueous solution" in the table means that deionized water is used in the system in which the concentration of the prepared Al aqueous solution is 0 mM, and the system is used in a system in which the concentration of the prepared Al aqueous solution is 2 mM and 20 mM. The Al solution will be described later.

[Adjustment of Al solution (aqueous solution of AlCl ₃ )]

After adding a predetermined amount of AlCl ₃ ‧6H ₂ O to distilled water and heating and dissolving it in an autoclave, an appropriate amount of KOH aqueous solution was added to adjust the pH to around 7.0. Thus, an aqueous solution of AlCl _{3 for} adding a medium having a concentration of AlCl ₃ of 2 mM and 20 mM was prepared. This AlCl ₃ aqueous solution was supplied to the method of Comparative Example 1.

[Adjustment of Al solution (chelating Al aqueous solution)]

After adding a predetermined amount of AlCl ₃ ‧6H ₂ O to distilled water and heating and dissolving it in an autoclave, adding a molar amount of lemon such as AlCl ₃ in the above aqueous solution to the heated AlCl ₃ ‧6H ₂ O aqueous solution Acid, and water, and stirred for 1 hour. Thereafter, an appropriate amount of KOH aqueous solution was added to adjust the pH to around 7.0. Thus, a chelating Al aqueous solution for adding a medium having a concentration of citric acid ‧ Al chelate of 2 mM and 20 mM was prepared. This chelated Al aqueous solution was supplied to the method of Example 1.

The concentration of oxalic acid ‧ Al chelate was prepared in the same manner as in Example 1 except that oxalic acid such as AlCl ₃ in the above aqueous solution was added to the aqueous solution of AlCl ₃ ‧6H ₂ O heated and dissolved in water A chelated Al aqueous solution was added to the medium of 2 mM and 20 mM. This chelated Al aqueous solution was supplied to the method of Example 2.

The concentration of the EDTA‧Al chelate was prepared in the same manner as in Example 1 except that the amount of EDTA, such as AlCl ₃ in the above aqueous solution, and water were added to the heated AlCl ₃ ‧6H ₂ O aqueous solution. A chelated Al aqueous solution was added to the medium of 2 mM and 20 mM. This chelated Al aqueous solution was supplied to the method of Example 3.

[Preparation of medium to which Al is added]

The AlCl ₃ aqueous solution or the chelating Al aqueous solution prepared as described above is added in Tables 1 to 3 which have been previously sterilized by an autoclave so as to have a composition ratio as shown in Tables 1 to 3. A medium to which Al is added is prepared as a component of the medium. The medium to which Al was added was adjusted to the pH values shown in Tables 1 to 3 by adding an appropriate amount of potassium hydroxide and hydrochloric acid.

[to cultivate]

In a sterilized 100 ml (nominal) vial, 100 ml of the above Al-added medium was injected, and the above-mentioned medium was blown with deoxidized nitrogen gas for a certain period of time, whereby the inside of the vial was anaerobic. In the cell culture medium at a concentration of 10 ⁶ cells implanted by each relay (sulfate reducing bacteria, coliform bacteria, butyric acid bacteria) of the culture. Thereafter, the vial was sealed with a butyl rubber stopper and an aluminum seal, and shake culture was carried out in an incubator at 37 °C. The shaking culture was carried out with the number of oscillations (110 times/min) to the extent that the hydroxide did not precipitate. Samples were taken from the culture solution and used for evaluation.

[Evaluation method (protein amount measurement)]

1 ml of the medium was taken from the vial, and the medium component was removed and suspended in 1 ml of sterilized distilled water. The protein was extracted from the suspension by an ultrasonic breaker, and the amount of protein was measured by the BCA method (diquinolinecarboxylic acid method). The growth inhibitory effect (bactericidal effect) of each of the cells was evaluated based on the amount of the protein.

[result]

Regarding the method of Example 1 (addition of citric acid ‧ Al chelate compound), a graph showing the bacteriostatic effect on the sulfate-reducing bacteria is shown in Fig. 1, and a graph showing the bacteriostatic effect on the coliform is shown in Fig. 2 . A graph showing the effect on the bacteriostatic effect of butyric acid bacteria is shown in Fig. 3. Further, regarding the method of Comparative Example 1 (addition of AlCl ₃ ), a graph showing the bacteriostatic effect on the sulfate-reducing bacteria is shown in FIG. 4 , and a graph showing the bacteriostatic effect on the coliform is shown in FIG. A graph showing the bacterial effect of the bacteria is shown in Fig. 6. In the graphs, the horizontal axis represents the elapsed time (unit: hour), and the vertical axis represents the logarithm of the amount of protein (unit: mg/L).

According to the method of Comparative Example 1 (addition of AlCl ₃ ), as shown in FIGS. 4 to 6 , the increase in the amount of protein was suppressed in all the culture solutions of the sulfate reducing bacteria, the coliform bacteria, and the butyric acid bacteria. That is, according to the method of Comparative Example 1, not only the proliferation of the sulfate-reducing bacteria was suppressed, but also the proliferation of the coliforms and the butyric acid bacteria was suppressed.

Further, according to the method of Example 1 (addition of citric acid ‧ Al chelate compound), as shown in Fig. 1, the increase in the amount of protein was suppressed in the culture solution of the sulfate-reducing bacteria. That is, the proliferation of the sulfate-reducing bacteria is suppressed.

On the other hand, as shown in FIG. 2 and FIG. 3, even if the Al chelate compound is added to the culture solution of the coliform and the butyric acid bacteria, the amount of the protein is increased as in the case of not adding. That is, the growth of coliform and butyric acid bacteria was not inhibited, and the selective bacteriostatic effect was observed in the method of Example 1. Further, although not shown in the graph, the method of Example 2 (addition of Al‧ oxalic acid chelate) and the method of Example 3 (addition of Al‧EDTA chelate) can be seen to be the same as in Example 1. Selective bacteriostatic effect.

[2] Examples 4 to 8, Comparative Examples 2 and 3 (gypsum composition): [Preparation of gypsum composition]

Gypsum compositions having the compositions described in Table 4 (Examples 4 to 8, Comparative Examples 2 and 3) were prepared. As the gypsum, calcined gypsum obtained by pulverizing waste gypsum and calcining it is used. As the Al ³⁺ source, AlCl _{3 was used} . As the chelating agent, citric acid is used.

100 ml of the medium described in Table 1 and 2 g of the gypsum composition of any of Examples 4 to 8 and Comparative Examples 2 and 3 were placed in a sterilized 100 ml (nominal) vial. Further, an appropriate amount of an aqueous calcium hydroxide solution was added to adjust the pH to 6.5. This pH adjustment is performed in order to prevent the culture solution from being biased toward the acidic side and becoming an environment in which the bacteria cannot survive.

Then, the inside of the vial was anaerobic by blowing a deoxygenated nitrogen gas in a vial for a certain period of time. Further, in the above medium at a concentration of 10 ⁶ cells implanted by the subculture of sulphate reducing bacteria. Thereafter, the vial was sealed with a butyl rubber stopper and an aluminum seal, and shake culture was carried out for 100 hours in an incubator at 37 °C. The shaking culture was carried out with the number of oscillations (110 times/min) to the extent that the hydroxide did not precipitate. Further, the above culture conditions are conditions in which hydrogen sulfide is easily generated in order to generate hydrogen sulfide. That is, the above culture conditions are not on-site reproducers such as soil modification sites or illegal disposal.

[Evaluation method (protein amount measurement)]

1 ml of the medium was taken from the vial, and the medium component was removed and suspended in 1 ml of sterilized distilled water. The protein was extracted from the suspension by an ultrasonic breaker, and the amount of protein was determined by the BCA method (diquinolinecarboxylic acid method). The growth inhibitory effect (bactericidal effect) of each of the cells was evaluated based on the amount of the protein. The results are shown in Table 5.

[Evaluation method (hydrogen sulfide production amount)]

The culture solution taken from the vial was filtered through a membrane filter having a pore size of 0.22 μm, diluted appropriately with distilled water, and the amount of hydrogen sulfide generated was measured by HPLC (High Speed Liquid Chromatography). As the HPLC, an HPLC system manufactured by Tosoh Corporation including a pump, a column heater, an anion analysis column, and a UV (ultraviolet) detector was used. The results are shown in Table 5.

The gypsum composition of Examples 4 to 8 was significantly reduced in the amount of hydrogen sulfide generated and the amount of protein compared with the gypsum composition of Comparative Example 2 (without addition of AlCl ₃ and Al chelate), and the proliferation of sulfate-reducing bacteria was suppressed. . Further, it is considered that the amount of hydrogen sulfide generated is not zero because a small amount of dissolved hydrogen sulfide is detected in the culture solution. Among them, the gypsum composition of Examples 5 to 8 (0.2 to 20 parts by mass of the Al chelate compound) can suppress the generation of hydrogen sulfide to a sufficient extent. In particular, the gypsum composition of Examples 6 to 8 (2 to 20 parts by mass of the Al chelate compound) can substantially completely suppress the generation of hydrogen sulfide.

Further, according to the data of the gypsum composition of Example 8, it is considered that when 10 parts by mass of the Al chelate compound is added, the generation of hydrogen sulfide can be sufficiently suppressed. Therefore, in view of the production cost, the gypsum composition of Examples 4 to 7 (0.02 to 10 parts by mass of the Al chelate compound) is preferable. In addition, it is preferable that the production of hydrogen sulfide is substantially completely suppressed, and the gypsum composition of Example 5 or 6 (0.2 to 2 parts by mass of the Al chelate compound) is further preferable.

On the other hand, the gypsum composition of Comparative Example 3 (0.002 parts by mass of the Al chelate compound) and the gypsum composition of Comparative Example 2 (without addition of AlCl ₃ and Al chelate compound), the amount of hydrogen sulfide generated and the amount of protein were both The decrease was confirmed, and the proliferation of the sulfate-reducing bacteria was confirmed to be suppressed. However, its effect is not sufficient.

Further, 100 kg of the gypsum compositions of Examples 4 to 8 were added to 1 m ³ of the soil having a water content of 40%, and then sufficiently kneaded and cured. As a result, the treated materials are all cured and have sufficient strength to withstand handling. In addition, it is confirmed that all of them are within the range determined to have no influence on the environment.

In addition, the gypsum composition of Examples 4 to 8 is a gypsum paste (described in JIS A6904), a joint treatment material for gypsum board (described in JIS A6914), or a gypsum board product (JIS). When it is recorded in A6901), it does not cause any problems on the production line. Further, the gypsum paste and the joint treatment material for the gypsum board are a gypsum composition of a powdery form, and are a gypsum-based solidified material which is cured by reaction with water. Further, the gypsum board product is a gypsum-based building material obtained by adding water to a gypsum composition, forming it into a plate shape, and solidifying it.

Further, it was confirmed that the gypsum compositions of Examples 4 to 8 did not adversely affect the properties or workability of the gypsum paste, the joint treatment material for gypsum board, gypsum board products, and the like. Further, the gypsum board or the gypsum paste produced by using the gypsum composition of Examples 4 to 8 as a raw material was subjected to the same test, and as a result, the generation of hydrogen sulfide was remarkably suppressed as compared with the conventional one.

(industrial availability)

The bacteriostatic method of the present invention can be used for inhibition of proliferation of a sulfate-reducing bacterium and further suppression of formation of hydrogen sulfide.

Further, the gypsum composition of the present invention can be preferably used as a gypsum composition, a gypsum-based solidified material, and a gypsum-based building material which can suppress the generation of hydrogen sulfide. More specifically, it can be used as a gypsum paste (coating material), a joint treatment material for gypsum board (soot), a solidified material for soil treatment (a solidified material for curing residual soil, sludge, mud, etc.), etc. Gypsum-based solidified material. also, It can be used as gypsum plate (including gypsum board), gypsum block, gypsum board for construction, and functional gypsum board for ceiling, wall and floor (for decoration, sound absorption, moisture absorption) Gypsum-based building materials such as functional gypsum board). Further, it can be used as another gypsum composition such as a wire for white wire, a fertilizer, and a rubble stripper.

Claims (4)

A selective bacteriostatic method for sulphate-reducing bacteria, characterized in that chelating Al is coexisted in an environment in which a sulphate-reducing bacterium of any one of Gram-negative bacteria, Gram-positive bacteria and archaea is present, The proliferation of the above-mentioned sulfate reducing bacteria is selectively inhibited. The selective bacteriostatic method according to the first aspect of the invention, wherein the chelating Al is formed in the environment by adding an Al ³⁺ source and a chelating agent in an environment in which the sulfuric acid reducing bacteria are present. The selective bactericidal method according to claim 2, wherein the Al ³⁺ source is selected from the group consisting of Al ₂ O ₃ , AlCl ₃ , Al(OH) ₃ and Al ₂ (SO ₄ ) ₃ . At least one Al compound. The selective bacteriostatic method according to the first aspect of the patent application, wherein the sulfuric acid reducing bacteria are bacteria that survive at 20 to 45 ° C and have a pH of 5 to 9.